1. Field of the Invention
The present invention relates to an active device array substrate and a repairing method thereof, and more particularly, to a thin film transistor array substrate and a repairing method thereof.
2. Description of the Related Art
A thin film transistor liquid crystal display (TFT LCD) mainly comprises a TFT array substrate, a color filter array substrate, and a liquid crystal layer. Wherein, the TFT array substrate is composed of a plurality of TFT arrays and pixel electrodes corresponding to each of the TFTs. A TFT serves as a switch of a pixel. In order to control the pixels, the scan lines and the data lines coupled to the TFTs are used to select a specific pixel. By applying a proper operational voltage, the data corresponding to the pixel can be displayed.
It is the trend that LCD panels are to be with high brightness, high contrast, large display size, and wide view angle. In order to improve the view angle of the LCD panel, several wide-view-angle techniques have been proposed. The popular LCDs with wide view angle include, for example, the multi-domain vertical alignment (MVA) LCD, the in-plane switching (IPS) LCD, and the fringe field switching (FFS) LCD. For an MVA LCD, plural slits are formed on the pixel electrode, for example. Plural protrusions are disposed on the color filter array substrate corresponding thereto. By matching the slits and the protrusions, liquid crystal molecules in the liquid crystal layer can tile in various directions and the wide-view-angle performance can be achieved.
Note that, in order to increase memory and maintenance functions of pixels for display data, portion of areas of pixel electrodes cover common lines to form metal-insulator-ITO (MII) storage capacitors Cst in the prior art technology. While forming data lines, sources and drains, a top electrode is disposed between each pixel electrode and a common line or scan line corresponding thereto. The pixel electrode and the top electrode are then electrically connected. The top electrode, the common line or scan line, and the dielectric layer between them constitute a metal-insulator-metal (MIM) storage capacitor.
FIG. 1A is a regional top view of a prior art TFT array substrate with an MIM storage capacitor. FIG. 1B is a cross-sectional view along the A-A′ shown in FIG. 1A. Referring to FIGS. 1A and 1B, a portion of a pixel electrode 150 is disposed over a common line 110 corresponding thereto. A top electrode 130 is disposed between the pixel electrode 150 and the common line 110 corresponding thereto. In addition, a dielectric layer 120 is disposed between, and isolates the top electrode 130 and the common line 110 corresponding thereto. Another dielectric layer 140 is disposed between the top electrode 130 and the pixel electrode 150 corresponding thereto. Wherein, the dielectric layer 140 comprises a contact hole 142 which allows the top electrode 130, through the contact hole 142, electrically connecting with the pixel electrode 150. Accordingly, the common line 110, the dielectric layer 120, and the top electrode 130 constitute an MIM storage capacitor 102.
During forming the prior art TFT array, failures of storage capacitors may occur due to defects or other reasons. Such failures will result in defective pixels. Please refer to FIGS. 2A-4A and 2B-4B. Wherein, FIGS. 2A-4A are drawings showing top views of prior art defective pixels. FIGS. 2B-4B are cross-sectional views along A-A′ shown in FIGS. 2A-4A.
Referring to FIGS. 2A and 2B, a defect 122 exits in the dielectric layer 120 between the common line 110 and the top electrode 130. The defect 122 can be, for example, a particle or a hole resulting from process contamination. The defect 122 results in charge leakage between the top electrode 130 and the common line 110. Referring to FIGS. 3A and 3B, while the data line 160 and the top electrode 130 are formed, a residue of a conductive material 170, such as aluminum, may be left between the data line 160 and the top electrode 130, so that the pixel electrode 150 is shorted to the data line 160 through the top electrode 130. Referring to FIGS. 4A and 4B, while the pixel electrode 150 is formed by the prior art technology, a residue of a conductive material 180, such as ITO, may be left between two neighboring pixel electrodes 150, and the neighboring pixel electrodes 150 are shorted. No matter what situation described above, the pixel cannot normally function, and the display quality of the LCD will be affected.